Peat disturbance, mowing, and ditch blocking as tools in rich fen restoration

Published source details Mälson K., Sundberg S. & Rydin H. (2010) Peat disturbance, mowing, and ditch blocking as tools in rich fen restoration. Restoration Ecology, 18, 469-478.
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This study is summarised as evidence for the following.

	Action	Category
	Disturb peatland surface to encourage growth of desirable plants (without planting) Action Link
	Cut/remove/thin forest plantations Action Link
	Use cutting/mowing to control problematic herbaceous plants Action Link
	Cut/remove/thin forest plantations and rewet peat Action Link
	Rewet peatland (raise water table) Action Link

Disturb peatland surface to encourage growth of desirable plants (without planting)

A replicated, randomized, paired, controlled, before-and-after study in 2002–2005 in two degraded rich fens in Sweden (Mälson et al. 2010) reported that disturbing surface peat changed plant community composition and cover. The cover results were not tested for statistical significance. Disturbance significantly altered the development of the plant community over three years (data reported as a graphical analysis). Disturbed plots consistently had lower cover than undisturbed plots of Sphagnum mosses (disturbed: 0–2%; undisturbed; 2–25%) and purple moor grass Molinia caerulea (disturbed: 1–9%; undisturbed; 23–50%). Cover of common reed Phragmites australis, sedges Carex spp. and common cottongrass Eriophorum angustifolium showed mixed responses to disturbance amongst sites, species or other treatments applied to plots. Seventeen fen-characteristic plant species colonized disturbed plots (data not reported for undisturbed plots). In autumn 2002, sixty-four 2.5 x 2.5 m plots were established (in four blocks of 16) across two degraded fens. Thirty-two plots (eight random plots/block) were cleared of vegetation and dug over (top 10–20 cm of peat disturbed). The other plots were not disturbed. Additionally, trees had been removed from all plots and some plots were rewetted and/or mown. In 2002 (before intervention) and 2005, cover of every plant species was estimated in one 0.25 m² quadrat/plot.

(Summarised by: Nigel Taylor)
Cut/remove/thin forest plantations

A replicated before-and-after study in 2002–2005 in two drained, tree-colonized, rich fens in Sweden (Mälson et al. 2010) reported that following tree removal, there were small changes in plant community composition and cover. These results are not based on tests of statistical significance. The overall composition of the plant community changed over three years following tree removal (data reported as a graphical analysis). Cover was reported for the most abundant plant species. For example, in one fen, Sphagnum moss cover was 43% before tree removal but 28% three years after. Cover of common cottongrass Eriophorum angustifolium was <1% before but 5% after. Across both fens, cover remained relatively stable for purple moor grass Molinia caerulea (before: 55%; after: 50%), common reed Phragmites australis (4% before and after) and sedges Carex spp. (0–1% before and after). In late 2002, all trees were cut and removed from two drained 50 x 150 m plots (one plot/fen). Vegetation cover was estimated before (2002) and after (2005) tree removal in 4–16 quadrats (each 0.25 m²) in the centre of each plot. This study was based on the same experimental set-up as (3) and (4).

(Summarised by: Nigel Taylor)
Use cutting/mowing to control problematic herbaceous plants

A replicated, randomized, paired, controlled, before-and-after study in 2002–2005 in two degraded rich fens in Sweden (Mälson et al. 2010) reported that repeated mowing altered the plant community composition, reduced cover of purple moor grass Molinia caerulea and increased overall cover of Sphagnum moss. The cover results were not tested for statistical significance. Mowing altered the development of the overall plant community over three years, although only significantly so in one fen (data reported as a graphical analysis). In three of four comparisons, mown plots had lower cover than unmown plots of purple moor grass (mown: 1–37%; not mown: 2–50%) but higher overall cover of Sphagnum moss (mown: 2–41%; not mown: 1–28%). However, cover of individual Sphagnum species showed mixed responses to mowing amongst sites or other treatments applied to plots. The same was true for sedges Carex spp., common cottongrass Eriophorum angustifolium and common reed Phragmites australis. In autumn 2002, sixty-four 2.5 x 2.5 m plots were established (in four blocks of 16) across two degraded fens. Thirty-two plots (eight random plots/block) were mown every autumn between 2003 and 2005. Cuttings were removed. The other plots were not mown. Additionally, trees had been removed from all plots and some plots had been rewetted or dug over. In 2002 (before intervention) and 2005, cover of every plant species was estimated in one 0.25 m² quadrat/plot.

(Summarised by: Nigel Taylor)
Cut/remove/thin forest plantations and rewet peat

A replicated before-and-after study in 2002–2005 in two drained, tree-colonized, rich fens in Sweden (Mälson et al. 2010) reported that following rewetting and tree removal, there were small changes in plant community composition and cover. These results are not based on tests of statistical significance. The overall composition of the plant community changed following tree removal and rewetting (data reported as a graphical analysis). In one fen, cover of purple moor grass Molinia caerulea was 50% before intervention but 30% three years after. Common cottongrass Eriophorum angustifolium disappeared (having had 0.1% cover before intervention). Across both fens, cover of sedges Carex spp. was 0–1% before but 1–8% after. Cover of common reed Phragmites australis and Sphagnum mosses showed mixed responses by site or species respectively. In plots that had trees removed without rewetting, moor grass and sedge cover changed much less than under the combined treatment, whilst cottongrass cover increased (from <1 to 5%). Around winter 2002/2003, two 50 x 150 m plots (one plot/fen) were cleared of trees and rewetted by blocking drainage ditches (water table raised approximately 10 cm). Two adjacent plots (one plot/fen) were cleared of trees but remained drained. Vegetation cover was estimated before (2002) and after (2005) intervention, in 4–16 quadrats (each 0.25 m²) in the centre of each plot. This study was based on the same experimental set-up as (6) and (8).

(Summarised by: Nigel Taylor)
Rewet peatland (raise water table)

A replicated, paired, controlled, before-and-after study in 2002–2005 in two degraded rich fens in Sweden (Mälson et al. 2010) reported that rewetting alone led to small changes in plant community composition and cover. These results are not based on tests of statistical significance. The overall composition of the plant community changed over three years following rewetting (data reported as a graphical analysis). Cover of sedges Carex spp. increased in rewetted plots (from 0–2% before rewetting to 1–8% three years after) but was stable in drained plots (0–1%). Purple moor grass Molinia caerulea was common in one fen, where cover decreased in rewetted plots (from 50 to 30%) but was stable in drained plots (50–55%). Sphagnum mosses were common in the other fen, where cover increased in rewetted plots (from 14 to 25%) but decreased in drained plots (from 43 to 28%) – although responses differed between species. In spring 2003, one 50 x 150 m plot in each fen was rewetted by blocking a drainage ditch (water table raised approximately 10 cm). An adjacent plot in each fen remained drained. Both plots were also cleared of trees. Vegetation cover was estimated, in 0.25 m² quadrats, in the central 100 m² of each plot: sixteen quadrats in 2002 across the whole 100 m², and four quadrats in 2005 within subplots that received no additional treatment. This study was based on the same experimental set-up as (18) and (23).

(Summarised by: Nigel Taylor)